For the first time, researchers have been able to drill deep (more than 1,600 meters) into an ocean fault zone.

The expedition team, onboard the Japanese research ship Chikyu, is searching for answers in the depths of the Nankai Trough about why the previously active fault has locked up in the past several decades—and what type of activity might be likely in the near future.

The Nankai Trough, off the southeast coast of Japan, is strikingly similar to the Cascadia subduction zone near the West Coast of North America, making more local researchers keen on the forthcoming data. “It’s almost as if we are drilling our own subduction zone because we’ll see a lot of the same things,” Kelin Wang of the Geological Survey of Canada told Wired.

Researchers on the expedition, which is part of the international Integrated Ocean Drilling Program, are using riser drilling to measure seismic data and collect core samples. The collected rock will help them understand what happened along the fault in the past.

Nankai was responsible for two magnitude 8-plus earthquakes and subsequent tsunamis in the 1940s but has been locked ever since, according to Wired. “We know that a locked fault is not a quiet thing, but we don’t quite understand why,” Wang told Wired. In the next 30 years, the Japanese government estimates, the fault has about a 60 percent chance of producing an earthquake bigger than magnitude 8, BBC News reported in May.

One of the chief scientists on the expedition, Eiichiro Araki of the Japan Agency for Marine-Earth Science and Technology, explained in a prepared statement that a system of sensors are being installed to act “like a telescope exploring the structure of faults in detail, which are responsible for causing large earthquakes.”

The team also hope the drilling will provide for a better understanding of how and when these ocean faults create tsunamis, like 2004’s Indian Ocean earthquake did, killing hundreds of thousands of people. And, according to the Wired report, the drilling itself won’t set off a quake.

Image of the Nankai Trough courtesy of Peka via Wikimedia Commons